I have a positive Tab S balance, a Nexus S, and a monthly plan. I would like to upgrade to a Nexus 4 using my positive Tab S balance to pay for most of its price and use that phone with my current monthly plan. I want to keep my old phone as a backup and simply take its Koodoo sim card out and place it within the new phone. Using the online store I cannot find a way to purchase the Nexus 4 without getting a whole new second plan. How do I buy a new phone using my positive Tab S balance online without purchasing a new plan so that I can use this new phone for my current plan?